Was it an accident that killed clarisse in Fahrenheit 451?

They say that yes, it was an accident. However, this may not be the case. Clarisse says that the kids in her class don't like her. She also says that children kill each other for fun. Later, Mrs. Montag suggests that Guy Montag drives the bullet car and run over some animals. Putting all of this together, it is likely that one of the kids in Clarrise's class killed her. Also, Captain Beatty says that her family was a problem, and that they were watching them. He also says that she was an odd duck and insinuates that they have to get rid of them. Beatty calls her a 'time bomb' and says that she's better off dead. It's possible that they killed her, either because she was a usurper, or because they considered it a mercy killing.

So, although it is ruled as an accident, as a reader one must consider that she was killed on purpose. Only the late Ray Bradbury could say for sure.